3-D or 2.5-D integrated circuit (IC) devices may include one or more semiconductor dies connected through an interposer die, which is then mounted on a package substrate. The semiconductor dies of the 3-D or 2.5-D IC devices may have different functionalities and may be located on the same plane or stacked on top of each other. Various configurations for 3-D or 2.5-D IC devices may be realized, depending on the package type and application of the 3-D or 2.5-D IC device.
Such interposer dies include signal interconnect paths that allow for the different semiconductor die in a 3-D or 2.5-D IC device to communicate with each other. Interposers are independently fabricated with those paths and semiconductor dies subsequently coupled to those signal interconnect paths through other signal interconnect components (e.g., pads, microbumps) located on/within the surface of the interposer.
Currently, very few mechanisms exist for testing the quality of signal interconnect paths of interposer dies prior to assembly (e.g., coupling semiconductor dies to the interposer die for forming a 3-D or 2.5-D IC device). Prior to packaging of the 3-D or 2.5-D IC device, the signal interconnect paths of the interposer die are only electrically accessible through certain signal interconnect components such as micro-bumps or pads for which conventional probes do not exist. While other mechanisms exist for testing certain quality characteristics of the interposer die, such mechanisms are insufficient.
One such mechanism involves performing an optical scan of the interposer die for identifying defects. Optical scans are capable of detecting large defects in the interposer die, but often overlook smaller defects that may cause open circuits or short circuits in the signal interconnect paths. Such optical scans also suffer from other disadvantages including slow speeds and high costs, thereby rendering them infeasible for testing for quality of signal interconnect paths interposer dies prior to assembly.
Another mechanism for testing the quality of interposer dies prior to assembly involves probing power and ground planes of the interposer. Power and ground planes of the interposer are typically accessible prior to assembly due to their larger sized contacts (e.g., probe-pads), and more isolated location on the interposer die. While probing power and ground planes of the interposer does provide some assurances as to the quality of an interposer prior to assembly, such testing neglects the quality of signal interconnect paths formed in the interposer. Even where power and ground planes are in acceptable condition, defective signal interconnect paths may still produce a non-functional or unreliable 3-D or 2.5-D IC device.